1. Field of the Invention
The invention concerns cooling devices for microwave circuits and, more particularly, a cooling device for microwave tubes, notably high-power klystrons.
2. Description of the Prior Art
It is usual to cool down microwave circuits and, in particular, power microwave tubes. It is standard practice to cool down various parts in the klystrons by arranging fluid circuits around certain parts. In particular, the collector, which receives the electron beam is cooled down. Cooling circuits are also provided for the various cavities and, in any case, for the output cavity where there is a greater possibility that the electrons will diverge and strike the walls of the cavity. To overcome this, the cavity is sheathed with a jacket within which a cooling fluid is made to circulate.
However, more generally, in cooling down a part, a first conduit is used for the inlet of cooling fluid coming from a fluid source, and a second conduit, separate from the first one, is used for the return flow of the fluid which gets heated after its passage around the hot part.
Until now, the levels of power applied, especially in klystrons, have not been high enough to necessitate a cooling down of the part corresponding to the output coupling, used to transfer microwave energy to a microwave waveguide. This coupling consists chiefly of a coaxial cable formed by a hollow, central conductor having a predefined thickness and length, and an external conductor, the diameter of this external conductor being, naturally, greater than the diameter of the central conductor. A vacuum is set up between these two conductors.